convert servo signal into on/off

[shaunjohnson]

i'm stuck for info and you guys are very smart when it comes to electrics so...
i want a horn...very useful when nitro-orientated marshals didn't see you shoot off the berm and go bush, costing you the race.

so i dug out my old servo control board that i converted into a simple ESC when i was 10y.o. it still worked, and since it was an ESC it drove the horn pretty well.
trouble is i was looking at it the other day and found it to be generating quite a bit of heat, i was worried at first that it may have killed the MMM's BEC but it seems to be ok so i removed it.

so down to buisness, can i convert the PWM of a servo signal (1-2ms ish range or whatever it is) into a simple on/off signal to turn on and off (and power if possible) my horn circuit?for either a simple buzzer to a small 555 timer circuit to make a louder horn.

any ideas fella's?
shaun